Are the connections on the yellow 130 gear motors labeled positive and negative?

Are the connections on the yellow 130 gear motors labeled positive and negative? I don’t see any related markings saying which is which?

Thank you,
yeto

Does it make a difference? Try it and if the motor runs the way you want it, you are all set. If not, reverse the connections.

Paul

yeto:
Are the connections on the yellow 130 gear motors labeled positive and negative? I don't see any related markings saying which is which?

Thank you,
yeto

No. The motors are bi-directional.

Small DC motors are almost always polarized, and will almost always be marked with either a + or a red spot.

The brush angle will be set so that one direction is preferred, so you'll notice a higher top speed in that direction
with no load.

It doesn't prevent the motor being used in the other direction, it just means a small difference in efficiency
in the "wrong" direction.

The reason this is done is that efficiency is greater at high speeds this way - for most uses of small motors this
is what you want.

The reason brush angle makes a difference is that the current in the windings is retarded in time by the winding
inductance, so advancing the brush angle switches the current earlier to help compensate and give a higher
current at the point its needed for maximum torque.

The thing most people notice is that using two of these gear motors left and right means one is forward and one
is backward, so that the robot tends to goes in circles without any control loop to correct it (although
variations in friction can also cause this problem)

Thank you. This is very helpful.